1. Field of the Invention
The present invention generally relates to a battery and a negative electrode plate for a battery. More specifically, the invention relates to a nickel-hydrogen battery and a negative electrode plate for a battery.
2. Description of the Prior Art
As shown in FIG. 8, a negative electrode plate 1 of a conventional nickel-hydrogen battery comprises a rectangular substrate 2 and a paste-like material 3 which is filled therein to be rolled and which contains an active material. The substrate 2 is formed from a porous plate, such as a mesh or punching metal plate, which is made of a nickel plated soft steel. The paste-like material 3 contains a hydrogen absorbing alloy, a conductive material, a binder and a dispersing agent.
In the negative electrode plate 1 of the conventional nickel-hydrogen battery, a collecting tab 5 is an elongated strip-like conductive plate extending longitudinal directions. As shown in FIG. 9, one end portion of the collecting tab 5 is welded to a substrate exposed portion 4, which is obtained by removing a part of the paste-like material 3 from a longitudinally extending edge of the substrate 2, so that the collecting tab 5 extends in directions perpendicular to the longitudinal directions of the substrate 2. The negative electrode plate 1 with collecting tab 5 thus formed is wound so as to form a cylindrical body 6 as shown in FIG. 10. Thus, there is obtained a structure wherein the collecting tab 5 protrudes from the bottom end face of the cylindrical body 6. Then, the collecting tab 5 protruding from the bottom of the structure is bent so as to extend along the bottom face of the cylindrical body 6 as shown by reference number 5a in FIG. 11. Then, the negative electrode plate 1 having such a structure that is shown in FIG. 11 is inserted into a bottomed cylindrical battery can 7 as shown in FIG. 12, to cause the bent collecting tab 5a to contact a bottom plate 8 of the battery can 7 in a conductive state. Thereafter, the open top of the battery can 7 is closed by a lid 9 including a safety valve as is well known to complete a battery.
There is also known a negative electrode plate 11 shown in FIGS. 13 and 14. The negative electrode plate 11 comprises a rectangular substrate 12 and a paste-like material 13 which is filled therein to be rolled and which contains an active material. Along the overall length of one longitudinally extending edge of the rectangular negative electrode plate 11, a substrate exposed portion 14 having no layer of the paste-like material 3 is formed. In the substrate exposed portion 14, a porous surface of the conductive substrate 12 is exposed in a strip shape. A collecting tab 15 comprises a laterally elongated strip-like conductive plate extending along the substrate exposed portion 14. As shown in FIG. 14, the collecting tab 15 is bonded to the surface of the substrate exposed portion 14 by welding or the like so as to extend in longitudinal directions of the substrate exposed portion 14. The collecting tab 15 is resistance-welded to a collector (not shown) (see Japanese Patent Laid-Open No. 2000-299100).
In the conventional electrode plates for batteries as shown in FIG. 8 and so forth, it is required to form the substrate exposed portion 4 in the substrate 2 to weld the one end portion of the collecting tab 5 to the substrate 2, so that there is a problem in that it is required to carry out a large number of steps.
As shown in FIG. 13 and so forth, it is also required to form the substrate exposed portion 14 having no layer of the paste-like material 3 along the longitudinally extending edge of the negative electrode plate 11 to weld the collecting tab 15 to the surface of the substrate exposed portion 14 by welding or the like, so that there is a problem in that it is required to carry out a large number of steps.